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Effect of pH on degradation of indigo carmine by multi-doped ZnO photocatalyst (initial dye concentration is 15 mg L⁻¹ and catalyst dose is 2 mg L⁻¹)
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Multi-doped photocatalysts are among the new class of materials employed for photocatalysis and as an antimicrobial agent. Lower band gap energy due to the metal dopant and lower electron–hole recombination because of non-metal dopant increase the overall efficiency of photocatalyst. Furthermore, these dopants directly influence optical shift, crys...
Citations
... At alkaline pH between 8.0 and 9.0, a decrease in the inactivation rate was observed. The decreased rate of photoinactivation in alkaline pH might be due to the electrostatic repulsion between bacteria and NCs (Shinde et al., 2020). However, at a pH range below 7.0, a decrease in the inactivation rate of 5.8% at pH 6.0, 9.06% at pH 5.0, 13.4% at pH 4.0, and 28.6% at pH 3.0 was observed. ...
... Subsequently, ZnO is a very attractive candidate in the field of photocatalysis because of its advantageous characteristics, including its non-toxicity, low cost, easy accessibility, and wide range of band-gap, especially in the near-UV-Vis region. ZnO is well-suited for solar-driven photocatalytic applications since it absorbs around 90 to 93% of the total solar energy in this area [39][40][41][42][43][44][45][46][47][48][49][50][51][52] . Carbon dots (CDs) are a novel category of carbon-based nanomaterials that possess a three-dimensional nanostructure and dimensions that are smaller than 10 nm [53][54][55][56] . ...
The development of photocatalytic powders to remove contaminants from air solutions is an important field of research in the field of environmental conservation. CD/ZnO-H400, a heterogeneous photocatalytic production, is utilized to degrade the reactive red dye and the antibiotic ofloxacin found in wastewater. This study explains the synthesis of carbon dots (CDs) derived from coconut air and zinc oxide (ZnO) using a hydrothermal method at a temperature of 180 °C with a duration of 4 h and subsequently calcinated at a 400 °C temperature for 4 h. This shows a significant improvement in photocatalytic performance due to improved delivery efficiency at the interface. The cost-efficient use of solar energy allows the comprehensive elimination of harmful pollutants through detoxification. The removal of the contaminant takes place through the first-order reaction, with RR141 showing the highest constant rate at 0.03 min⁻¹, while ofloxacin has a constant speed at 0.01 min⁻¹. The photocatalytic stability is measured after five cycles. The study also tested the impact of sunlight on degradation, showing a degrading rate of 98% for RR141 and 96% for ofloxacin. This study displays a new catalyst powder synthesized from carbon dots derived from the air, coconut and ZnO, showing remarkable photoactivity to completely remove harmful dyes and antibiotics from the surrounding environment.
... Indigo blue is the main component of denim-washing wastewater (Paul 2015;Valdez-Vazquez et al. 2020). This dye prevents the penetration of light and oxygen into water bodies necessary for aquatic life (Shinde et al. 2020). Dye degradation by microorganisms under anaerobic conditions can generate aromatic amines that can be carcinogenic and mutagenic (Gürses et al. 2021), which represents a risk to aquatic life and public health. ...
Coagulation–flocculation is one of the most mature and effective process, which can remove most of the colloids. The objective of this study was to investigate a treatment for denim-washing wastewater by coagulation–flocculation and Fe/garnet filtration to evaluate the potential use of the sludge produced. The reaction time, stirring rate, dose, and coagulant agent using Ca2+, Mg2+, and Fe2+ as chlorides on the % removal of color, chemical oxygen demand, and turbidity were evaluated using an experimental design 32. The best chemical oxygen demand (49% of these low efficiencies may be related to chloride interferences), color (84.6%), and turbidity removal (82.3%) efficiencies were achieved at a dose of 1.4 g/L Ca2+, time of 20 min, and shaker speed of 50 rpm. Under these conditions, Ca(OH)2 commercial (Calidra® at 75–85%) was also tested, removing chemical oxygen demand, turbidity, and color by 67, 97, and 93%, respectively, at 1.4 g/L Ca2+. The effluent from the garnet filtration process was characterized, the pH was reduced from 11.8 initial to 7.7 final, and removals of 59.0% total organic carbon, 20.5% chemical oxygen demand, and 28.6% color. The effect of sludge from the coagulation–flocculation process with Ca(OH)2 was studied in Lactuca sativa seed. The life cycle assessment concluded that the treatment reduced the midpoint impacts of the environmental category indicators, such as freshwater eutrophication, marine eutrophication, freshwater ecotoxicity, marine ecotoxicity, human noncarcinogenic toxicity, land use, and mineral resource scarcity. Treated wastewater can be reused in the same process for denim washing.
... This study demonstrated that low pH and low temperature have an impact on the decomposition of microplastics, and the maximum degradation rate of high-density polyethylene microplastics could be achieved by optimizing the operating conditions. Zinc oxide (ZnO) is also one of the most promising contenders in the field of photocatalysis, with a wide forbidden band range near the ultraviolet-visible spectroscopy region, accounting for 90% to 93% of the total solar radiation (Shinde et al. 2020). Tofa et al. (2019aTofa et al. ( , 2019b synthesized ZnO nanorod and platinum (Pt) nanoparticles modified ZnO nanorods by hydrothermal method and used for the photocatalytic depolymerization of low-density polyethylene film in aqueous media. ...
Substantial quantities of discarded plastic have resulted in detrimental effects on the environment and ecosystems, calling for effective recycling of plastic wastes. Chemical methods for managing plastic wastes have been extensively studied, and selective recycling of products has grown in popularity. Pyrolysis, photocatalysis, and supercritical fluids were the main chemical methods reported for processing plastics. This article reviews reaction mechanisms and representative studies of pyrolysis, photocatalysis and supercritical fluid disposal of plastics. Three challenges are identified: first, high temperatures, above 400 °C, pose safety risks and potentially release harmful gases. Second, the photocatalytic decomposition of plastics is generally economical and environmentally friendly, however, reaction rates are uncontrollable. Third, the exceptional solubility and mass transfer properties exhibited by supercritical fluids have the potential to significantly augment the decomposition of plastics. Supercritical fluids can also serve as reactants that directly influence the thermal or kinetic mechanisms of the reaction. Whereas individual treatment methods are limited, coupled methods enable efficient plastic management and facilitate the selective acquisition of products. In particular, this review suggests that coupling photocatalysis and supercritical carbon dioxide should allow to dispose of plastics and convert carbon dioxide into valuable resources.
... Several methods for calculating the bang gap energy using optical absorption measurements have been suggested [19]. In this study, the optical band gap of Gd-doped ZnO nanomaterials is calculated using the Tauc's formula as given below [49]: ...
The synthesis and study of doped semiconducting nanomaterials have drawn great importance to researchers over the last few years. In the present study, we premeditated the structural, morphological and optical properties of gadolinium-doped zinc oxide (GZO) nanomaterials. The GZO powders were synthesized by modified solvothermal method by doping with Gd at 80 °C and characterized by XRD, FTIR, UV–Vis, SEM–EDX, TEM, SAED and HRTEM. The GZO with 5% doping of Gd exhibited maximum diffraction peak intensity. The XRD results exhibited that the crystallite size of Gd-doped ZnO nanomaterials was varied with Gd doping. The size of crystals first decreased then increased (50, 39 and 44 nm) with increasing the percentage of Gd from 5 to 15%, demonstrating the propensity of considerable grain growth in the nanomaterials due to doping of a high percentage of Gd. The morphology displayed by SEM and TEM micrographs is almost the same as irregular spherical shapes and small tiny particles on the surface of ZnO, which twisted into larger spherical ones with increasing Gd percentage. The optical band gap ranges from 2.87 to 2.93 eV with increasing the doping concentration of Gd, which reflects that the optical properties are affected by the doping of Gd.
... The net surface charge amount at this pH point of the SnO 2 -Fe 3 O 4 @MWCNT nanocatalyst particle is zero. If the pH of the reaction medium is below 7.86, the surface charge of the nanocatalyst particle is positive, and over 7.86, the nanocatalyst surface charge will be negatively charged [50,51]. Considering these data of pH experiments, the optimum pH value for MB degradation was determined to be 8. ...
In the present work, SnO2-Fe3O4@MWCNT nanocatalyst was fabricated according to a sonochemical-hydrothermal procedure. The surface morphology and structure analyses of the synthesized SnO2-Fe3O4@MWCNT were investigated by transmission electron microscope (TEM), X-ray diffraction (XRD), Raman spectroscopy, EDS, FTIR and BET analyses. The degradation efficiency of SnO2-Fe3O4@MWCNT nanocatalyst in MB solution was tested by several experimental conditions such as SnO2-Fe3O4@MWCNT dosage (8–20 mg/L), initial MB concentration (20–50 mg/L), initial solution pH (5–9), and ultrasonic output power (37–60 kHz). SnO2-Fe3O4@MWCNT nanocatalyst retained its efficiency as 85% at common experimental conditions of 16 mg/L of SnO2-Fe3O4@MWCNTs, 45 mg/L of MB, pH of 8, H2O2 of 15 mM, and 60 kHz in 60 min under ultrasonic irradiation. In addition, the optimum experiment conditions for SnO2-Fe3O4@MWCNTs in MB degradation were investigated. The experiment result showed that the degradation efficiency of MB was increased by adding H2O2 to the reaction medium due to forming more free radicals. Further, it was detected that OH• radicals were determined to be the dominant oxidative species in MB degradation using SnO2-Fe3O4@MWCNT catalyst. The reuse tests showed that SnO2-Fe3O4@MWCNT sonocatalyst preserved its very stable structure after using the same catalyst 5 times. The intermediates and by-products after MB degradation using the catalyst were indicated by GC–MS analysis. Overall the results showed that the SnO2-Fe3O4@MWCNT sonocatalyst has excellent potential for treating organic pollutants in wastewater.
Graphical Abstract
... The improvement in optical properties because of the ZnO/CuO heterostructure has been lost here which is reflected in the photocatalytic study as well. In the literature, the band gap of ZnO/CuO, developed through solution-based coprecipitation method has been observed to be in the range of 2.34-3.25 eV [57,58]. The optical band gap of Ni_ZnO/CuO_25 and Cu_CuO/ZnO nanocomposite, developed in the current study is 2.48 eV and 2.95 eV, respectively. ...
In this work, we report the fabrication of Ni and Cu tubular substrates and the synthesis of ZnO/CuO nanocomposite on them through the process of pulse electrodeposition. The systematic variation in CuO incorporation in the ZnO matrix and the processing technique were noticed to affect the structural, optical, photocatalytic, and anti-bacterial properties, which are well in accordance with the Field Emission-Scanning Electron Microscope, X-ray Diffraction, Fourier transform Infrared Spectroscopy and UV-Differential reflectance spectroscopy results. The remediation capabilities of the photocatalytic substrates were assessed through the degradation of Methylene blue (MB) dye under solar irradiation. Optimized CuO incorporation within the ZnO nanorods resulted in the degradation of a 20 ppm of MB dye solution within 40 min and a higher concentration of 50 ppm within 95 min. The Ni and Cu electroformed tubes as substrates provided not only a reusable supporting frame but also a large surface-area for the growth of ZnO/CuO nanocomposite. The current study also dealt with the anti-bacterial efficacy of the above-mentioned substrates against E.coli. Hence, the Ni and Cu tubular thin film substrates with nanorods of ZnO/CuO composite were explored for the removal of organic as well as biological contaminants from waste water.
... Numerous metals, such as Cu, Fe, Al, Nd, Gd, Ag, Sn, Mn, In, Mg, Au, Ti, and others, are recurrently used as doping agents in ZnO, but nickel is found to be effective dopant as it promotes visible light absorption by bringing down the band gap, emits electron-hole pairs, declines the recombination of these photo-induced charge carriers, provides strength and stability, improves morphological characteristics, and endorses the principal metal oxide for the photocatalytic degradation [38,41]. A base metal oxide's energy levels are unaffected by a dopant concentration that is too low and on the other hand its original nature is altered by a dopant concentration that is too high. ...
... Fig. 12 shows the reusability findings while using EB dye. Fig. 13 depicts a possible photocatalytic reaction pathway for dye degradation utilising Ni/ZnO as per previously reported literature [41]. The active species in the photocatalytic degradation of EB dye solution include hydroxyl radicals, photogenerated holes, and superoxide radical anions. ...
This article describes the fabrication of ZnO and 5% Ni²⁺ modified ZnO nanocatalyst (Ni/ZnO) for the photocatalytic degradation of eosin blue (EB) dye. To demonstrate the successful formation of nanocatalyst and study the structural and morphological aspects, as well as the chemical compositions, we employed X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) techniques. The optical band gap was investigated using Ultraviolet-visible (UV-Vis) spectroscopy, whereas the Zn-O band was revealed using Fourier transform infrared (FTIR) spectroscopy. To illustrate the optimized photocatalytic conditions for the degradation of EB dye, the parameters like initial EB dye concentration, catalyst loading, pH effect, and contact time were investigated. When compared to undoped ZnO and other reported nanocatalyst, the Ni/ZnO nanocatalyst displayed significantly better photocatalytic performance in the photocatalytic degradation of EB dye. With 0.8 g/L catalyst loading, 110 min contact period, and 8.0 pH, the photocatalytic efficiency was higher. Under optimized photocatalytic conditions, the results suggested that a Ni/ZnO nanocatalyst could be a potential nanomaterial for developing an enhanced doped nanocatalyst for EB removal. To confirm the presence of reactive oxygen species during photocatalysis, a radical scavenging experiment was performed using benzoquinone and isopropyl alcohol scavengers. The reusability of the produced nanocatalyst for four cycles confirms its stability and efficiency over multiple cycles. Furthermore, the Ni/ZnO was found to have significant antibacterial action against Staphylococcus aureus.
... The various metal, metal oxide and carbon based materials have been effectively used by many researchers for the degradation of various hazardous dyes, detection and remediation of environmental pollutants and chemicals like terephthalic acid, tetracycline, of Rhodamine B Congo red azo dye, crystal violet dye, Rosaniline hydrochloride dye, erythrosine, acid brown 14, eosin Y, Acid Yellow 23, Acid red 14, eriochrome cyanine R, eriochrome black T, carbol fuchsin, etc. [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64]. Besides, the undoped and doped metal oxides have been found to show effective gas sensing applications to monitor various greenhouse gases, industrial pollutants and hazardous laboratory gases [65][66][67][68][69][70]. ...
... 88-1007) phases (Mahmood et al. 2013;Jayakumar et al. 2011). In addition, the doped product's peaks at (2θ values) 17.24°, 23.50°, 44.21°, 61.27°, and 64.77° indexed to (100), (011), (112), (311), and (023), respectively, attributed to tetragonal and monoclinic ZrO 2 (JCPDS No. 81-1319) phases and the enhance in peaks (weak and sharpness) attributed the shifted toward polycrystallinity of samples (Jayakumar et al. 2011;Shinde et al. 2020a). ...
... Moreover, an observable shift to a higher (2θ) angle side was found after the addition of Mg, Mn into the ZrO 2 host matrix and this shift slightly increase with increasing the Mg, Mn concentration. These shifts may be attributed to the addition of Mg 2+ (0.72 Å), Mn 2+ (0.67 Å) by Zr 4+ (0. 84 Å) of greater ionic radius (Shinde et al. 2020a). The crystallite size (D) of pristine and co (Mg, Mn)-doped ZrO 2 samples was computed according to Scherrer's Eqn (Shinde et al. 2020b). ...
In this research, pristine and co (Mg, Mn)-doped ZrO2 products were successfully synthesized by the chemical co-precipitation route. The diffraction patterns of the pure ZrO2 affirmed the formation of the tetragonal phase. Dopant (Mg, Mn) induced phase change from the tetragonal to the monoclinic structure. UV–Vis absorbance spectrum revealed considerable tuning of energy gap from 2.99 to 2.65 eV with Mg, Mn doping due to surface defects. The co (Mg, Mn)-doped ZrO2 products showed important photocatalytic activity performance when irradiated with sunlight. The excellent photocatalytic efficiency, 94 and 96%, for both (MV and MB) dye substances degradation, was attained through Mg (0.08 M)- and Mn (0.08 M)-doped ZrO2 catalyst under sunlight illumination time of 70 min. The photodegradation was additionally confirmed by scavenger study and COD analysis. The reusing catalytic capability of the Mg (0.08 M)- and Mn (0.08 M)-doped ZrO2 product was also assessed with a slight diminish in the removal efficiency even after the six successive runs.
